Severe Respiratory Distress Syndrome suddenly emerged as an international threat in 2002-2003. Little is known about its natural history or management. A protocol has been developed and approved to bring patients to the Clinical Center to study the natural history of this disease, with special emphasis on duration of viral shedding and host response to the virus. This patient is open to enrollment should the disease reappear. In addition, an IRB and FDA approved protocol in currently underway in Hong Kong to collect source plasma from subjects that recovered from SARS and manufacture into a polyclonal IVIG. This project is in collaboration with the Chinese University of Hong Kong. The protocol remains open in case SARS reappears in humans. No cases have been seen worldwide since 2003